an airplane using 20 TR bootstrap air refrigeration system has ambient conditions of 0.9 bar and 15C. Ram air pressure after isotropic compression is 1.1 bar.

Main compressor exit pressure is 3.5 bar, and exit pressure of secondary compressor exit pressure is 4.5 bar. The cabin is required to be maintained at 1 bar and $25^o$C. Isentropic efficiency of each compressor is 85% and that of cooling turbine is 90%. The effectiveness of both heat exchangers is 60%. Find:

i) Mass flow rate of air passing through the cabin

ii) Power required

iii) COP of the system. Assume Cp = 1.01 KJ/KgK.

1 Answer

T1 = 15+273 = 288K

Consider the ramming action: ${T_2/T_1 }$=$(p_2/p_1 )^{(1.4-1)/1.4}$


$T_2=305 K$

Consider the main compressor:

${T_3/T_2} =(p_3/p_2 )^{(γ-1)/γ}$


${T_3=424.5K}$ enter image description here Fig.1 Process of Air refrigeration.

Efficiency of compressor I:

part1 part2

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